If called multiple times for the same build, do not delete the old artifacts but keep them all, unless overwritten.
For example, the XVNC plugin could use this to save screenshot.jpg if so configured.

This method is typically invoked on a running build, though e.g. in the case of Maven module builds,
the build may actually be Run.State.COMPLETED when this is called
(since it is the parent build which is still running and performing archiving).